This invention relates generally to a liquid-cooled four-valve cylinder head for a multi-cylinder internal-combustion engine.
In the case of a known cylinder head as disclosed in German DE-AS No. 24 20 051, the cylinder head bottom is supported essentially only by the transversely extending supporting walls from the cylinder head ceiling. As a result, critical stress conditions occur in the combustion chamber sections and particularly in the valve webs because of high gas pressures as well as high combustion temperatures, that may lead to web breaks and deflections of the cylinder head bottom. An additional fact is that the forces of pressure from the cylinder head screws are introduced into the cylinder head bottom only by the supporting walls. This makes it impossible to favorably distribute the pressure forces to other cylinder head walls and to evenly press the cylinder head to the cylinder housing.
An objective of the present invention is the provision of a cylinder head having a simple construction as far as casting practice is concerned which exhibits better rigidity and strength of the head.
Another objective is to provide a better reinforcement of the sections of the cylinder head bottom on the side of the combustion chamber.
An even further objective is to achieve a good distribution of the forces of pressure introduced into the bottom.
These and other objectives of the present invention are attained by the provision of a cylinder head for a multi-cylinder internal-combustion engine having a cooling water space delimited by lateral exterior walls, a cylinder head bottom and a cylinder head ceiling located at a position above the cylinder head bottom. A control space located above the cylinder head ceiling is delimited by the cylinder head ceiling, the exterior walls and a cover-separating plane. Valve ducts project into the cooling water space and lead away from mouth openings in the cylinder head bottom to the lateral exterior walls. A tube-shaped chamber for a spark plug or an injection nozzle extends between the valve ducts through the cooling water space axially to the cylinder. Supporting walls extend inside the cooling water space in a transverse direction between the combustion chamber sections of the cylinder head bottom and extend from the cylinder head bottom and extend from the cylinder head bottom to the cylinder head ceiling. The supporting walls are provided with molded-in supporting columns for bores which receive the cylinder head screws. A longitudinal rib provided as part of the cylinder head ceiling extends over the length of the cylinder head and is interconnected with the tube-shaped chambers and the supporting walls. The supporting walls are further supported at the cylinder head bottom by longitudinally extending rib webs which overlap into adjacent combustion chamber sections.
By means of the longitudinal rib in the cylinder head ceiling and its connecting to the tube-shaped chamber of the spark plug, a reinforcement of the cylinder head is achieved, particularly with respect to the bottom sections on the side of the combustion chamber. In connection with the rib webs, a favorable distribution is obtained in this case of the tension forces introduced by the tightening screws by the supporting columns into the cylinder head bottom and of the gas forces affecting the bottom section of the combustion chamber. On the one hand, these are absorbed by the chambers and the longitudinal rib and, on the other hand, by the rib webs and the supporting walls connected with them, achieving a rigid connection between the cylinder head bottom and ceiling. As a result, an even engagement of the cylinder head against the cylinder block is attained.
In a further advantageous development of the present invention, the cylinder head ceiling consists of two ceiling sections extending in a longitudinal direction relative to the cylinder head. These two ceiling sections interconnect with the longitudinal rib and are connected with the rib at different vertical points on the rib.
In another advantageous embodiment of the invention, one ceiling section slopes downward from the exterior wall toward the longitudinal rib and interconnects with the longitudinal rib at the bottom portion of the rib. The other ceiling section has a slope essentially equal to that of the first section and interconnects with the longitudinally extending rib at a top portion of the rib.
By means of these advantageous developments, the longitudinal rib can be integrated into the ceiling sections of the cylinder head ceiling in such a way that it has a smooth surface on both sides. The "step" that in the process is formed by the longitudinal rib will by no means interfere with the lubricating-oil return flow from the control space or the water flow in the water space because the oil drain from the control space as well as the cooling-water feeding into the water space in each case takes place via corresponding openings in the ceiling section that is located at a lower level. By means of a course of the ceiling sections that, on the whole, rises continuously, vapor bubbles can completely be discharged from the water space via the outlet openings arranged in the area of the ceiling section that is located at a higher level.
In another advantageous development of the present invention, the cylinder head ceiling, when installed in the engine, advantageously has an approximately horizontal orientation.
In another advantageous development of the present invention, the valves of the internal combustion engine are disposed in a V-shape and arranged in two rows on both sides diagonally to the central longitudinal plane. Two cam shafts are located approximately in the planes of the two valve rows of both the valves. These cam shafts are disposed in bearing seats molded into the external surface of the control space on each side of the central plane. The bearing seats are arranged in the vertical transverse plane of the supporting walls and the dividing plane of the bearing seats is coplanar with the cover-separating plane. Supporting columns extending to the cover-separating plane together with transverse connecting webs extending between the supporting columns combine to form a transverse interconnecting support structure. It is also contemplated that the transverse interconnecting support structure be reinforced by at least one rib extending in the direction of the longitudinal axis of the cylinder and interconnected with the tube-shaped chamber.
By means of this advantageous construction, especially in the case of a cylinder head having two rows of valves extending in a V-shape with respect to one another and two camshafts disposed in the control space, an increased rigidity of the control space area is achieved in addition to the desired increased rigidity of the cylinder head bottom.
In another advantageous of the present invention, the supporting walls are provided with break-throughs on both sides of the supporting columns. By means of these break-throughs, in addition to an unhindered distribution of the respective liquids in the longitudinal direction of the cylinder head, a favorable design of the water and oil cores is achieved with respect to casting and functional aspects.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, and embodiments in accordance with the present invention.